The integration of two different types of mobile radio transceivers, for example based on a Standard from the IEEE 802.11 Working Group (for example IEEE-802.11b)—referred to for simplicity in the following text as the IEEE-802.11 Standard or with the attribute WLAN (Wireless Local Area Network)—and the Bluetooth Standard in one appliance can lead to interference with the two transceivers in one direction or mutually. Particularly when the two transceivers are using the same or intersecting frequency ranges, their simultaneous radio activity can have a negative influence on the transmission behavior of one or both transceivers. If both transceivers transmit at the same time, the two transmitted signals are superimposed and can be separated by the corresponding communication partners only with difficulty. If one transceiver is transmitting while the other transceiver is receiving, the reception sensitivity is considerably restricted because of a poor antenna isolation. A similar influence can also be seen when the frequency ranges of the two transceivers are located very close to one another since, in this case, the sidebands interfere with the transmission behavior.
The influence of the interference at one end or mutual interference can be reduced by suitable restriction of the respectively used frequency ranges or by time coordination of the radio activities. Measures such as these for coordination of the radio activities are also referred to as co-existence or interoperability measures. The influence of interference at one end or of mutual interference can be virtually precluded in particular by time coordination of the radio activities. In order to allow time coordination of the radio activities, cable-based information interchange is necessary between the two transceivers or between each of the transceivers and a common device, in particular a common main processor (host), which controls the coordination process. The interchanged information is used to decide which of the transceivers may carry out radio activities, and which of the transceivers must delay or terminate the radio activities.
Basic recommendations for the co-existence of two transceivers are described in the provisional IEEE Standard Document IEEE P802.15.2/Draft #09, Mar. 24, 2003.
The document EP 1 119 137 A1 discloses an appliance in which both a Bluetooth transceiver and an IEEE-802.11 transceiver are integrated. In order to avoid interference caused by simultaneous radio activities by both transceivers, this document proposes that a so-called interoperability device be provided for time coordination of the radio activities. In this case, the interoperability device monitors the data flow between each of the two standard-specific drivers, the Bluetooth driver and the WLAN driver, and the transceiver elements which are associated with the physical interface. The interoperability device prevents the two transceivers from transmitting at the same time. It optionally prevents one transceiver from transmitting when the other transceiver is receiving or transmitting at the same time. This procedure makes it possible to ensure that the functionality of the two transceivers is fundamentally maintained, even in very poor environmental conditions or in critical applications. Time coordination of the radio activities of the two transceivers in this way has the disadvantage that, in many applications or operating situations, in which there is no evidence of the influence of interference at one end or mutually, the transmission capacity of one transceiver or of both transceivers is unnecessarily reduced by the coordination of the radio activities.